Multilayer Thermoformable Materials and Sanitary Food Containers Made Therefrom

ABSTRACT

A multilayer stack of polymeric sheets can be used in thermoforming processes to make objects wherein each sheet has substantially the same shape. The stack includes at least one sheet of a thermoformable polymer, and can include many such sheets. A barrier layer is interposed between at least an overlapping portion at least two of the polymeric sheets in order to prevent fusion of the sheets in the overlapping portion during the thermoforming process. The barrier layer can include an adhesive that adheres the sheets in the overlapping portion. In formed articles including such an adhesive, the sheets can be manually peeled from one another if a suitable adhesive is selected. The stack (and object formed using the stack) can include polymeric sheets that are not thermoformable, but are adhered to the surface of a thermoformable sheet. The sheets and objects can include multiple separable and/or peelable sheets. The stack can be used, for example, to make peelable, re-usable food service trays. In such trays, a rigid base has multiple peelable sheets adhered to at least one surface thereof, the sheets being peelable from the surface to reveal a sanitary surface amenable to food contact.

BACKGROUND OF THE DISCLOSURE

This disclosure relates generally to multiple-polymeric-layerthermoformable materials and articles formed from such materials. In oneaspect, the present disclosure relates generally to containers forhygienically containing food, including containers having multiplepeelable layers on a surface which contacts the food, such that the samecontainer can be used multiple times to hygienically contain foodwithout the need to sanitize the food-contacting surface between uses.

The disclosure also relates to other containers having peelable surfacelayers, such as paint trays.

Paint Trays

Paint is commonly applied to walls and other surfaces with a paintroller comprised of a roll of napped textile material or other paintabsorbent substrate carried on a handle, and a metal or plasticpaint-holding tray into which the roller is placed to load the roll withpaint. While useful in quickly applying a uniform paint coating to largesurfaces, a major disadvantage of the use of this system is the requiredmessy and time consuming chore of cleaning the roller and tray afteruse. The present application relates to an improved tray that enablesthe user to avoid tray cleaning, and to a tray with two wells divided bya flat section designed specifically to properly distribute paint on theroller nap. The tray configuration is also designed to lend itself tothermoforming.

In an attempt to minimize cleaning, the prior art describes a preformedpaint tray liner that is placed into the interior of a paint tray.Generally, these liners are thermoformed from a plastic sheet having athickness of from about 0.008 to about 0.03 inches. The paint is pouredinto this liner, which is removed and discarded along with any adheredpaint after the paint job is completed. While effective in eliminatingthe need to clean the paint tray, these preformed liners aresufficiently expensive that many users attempt to clean and reuse theliners. Their thickness adds significantly to environmental waste upondisposal and require significant amounts of energy to produce. Thepreformed tray liners also require separate additional storage prior touse.

Other prior art as exemplified by U.S. published patent application no.2004/0112902 to Campbell and U.S. published patent application no.2006/0037960 to Rosa manually presses an impervious plastic sheet havinga thickness of from about 0.5 to about 5 mils and an adhesive backinginto a previously formed paint tray so that the sheet approximatelyconforms to the tray. The sheet is peeled away and discarded after use.While using less material than preformed tray liners, these sheets areawkward and time consuming to individually hand press into place and donot provide a functional liner that exactly conforms to the trayinterior, especially in the corners of the tray.

Food Service Containers

Food is commonly held in bins, trays, pans, and other containers duringits preparation, presentation, and serving. In order to minimizetransmission of food-borne illnesses and to comply with applicableregulations regarding food sanitation, food and food-implementcontainers must be frequently sanitized. This is particularly true insituations in which food containers are used over long periods,refilled, or accessed frequently by individuals removing itemstherefrom. Examples of containers of these types include pans used inbuffet or steam tables, bins recessed in a food preparation surface,salad bar pans, bulk condiment containers, cutlery bins, hot and coldsoup kettles, and chafing dish inserts. In food service settings, it isdesirable to maintain hygienic conditions even for containers that donot hold food or implements intended for human consumption (e.g., binsused for busing tables and other utility bins).

Some food service situations require use of many food storage containersto separately contain different food items. Examples of such situationsinclude salad and buffet displays at restaurants, cafeterias, andgroceries at which customers select food desired for purchase from thecontainers. Other examples include food preparation stations (e.g., foodpreparation tables such as those shown in U.S. Pat. No. 6,385,990)located in restaurant, cafeteria, or grocery settings, at which anemployee of the establishment selects food (e.g., sandwich componentsand condiments) from a variety of trays accessible to the employee inresponse to requests from a customer. In these settings, containershaving standardized sizes are frequently used to facilitate replacementof a used container with a fresh one. Retailer food service practices orgovernment regulations often specify how frequently used containers mustbe sanitized or replaced, rather than simply refilled with new fooditems or implements. Frequently, the containers are not refilled, andare instead removed and sanitized prior to being refilled with food andreused, or are simply discarded.

Food storage containers are used to hold foods that must be maintainedat cool temperatures (e.g., perishable products such as meats, cheeses,lettuce, tomatoes, and yogurts), foods that are maintained at warm orhot temperatures (e.g., soups or cooked entrees), and food service itemsthat are maintained at ambient temperatures (e.g., breads and crackers,eating utensils, and foods intended for near-immediate consumption). Forfood storage containers in which heat transfer (either into or from thefood contained therein) is desired, it is known to make the containersfrom materials that exhibit thermal conductivity and heat capacitycharacteristics suited to the desired use of the container.

Conventional food service containers have a variety of shapes, such asrectangular and circular pans having an open top. A flange or rimtypically extends around the perimeter of the open pan top to hold thecontainer in a fitting, such as a frame or rack. When used in a heatedor chilled table setting, the flange can also provide a seal around theperimeter of the container, improving energy efficiency (i.e., bypreventing loss of heating or cooling medium) and appearance. The flangecan also act as a convenient surface for lifting, supporting, andcarrying the container. When used in a steam table, buffet table, saladbar, or the like, the body (e.g., the portion containing the food) andflange of a container are typically dimensioned so that the body of thecontainer is received into an opening in the table or bar and issupported by its flange resting upon the edges of the table or baropening or upon a frame or rack fitted to the bar or table.

Food storage containers sometimes have corresponding lids that areadapted to fit an orifice of the container (e.g., a soup tureen having afitted lid, optionally with a recessed section to accommodate the handleof a ladle when the tureen and lid are assembled). The lid can serve toexclude contaminants, to prevent gain or loss of heat, or somecombination of these functions.

Reusable food service containers of these types are made from a varietyof materials, and are frequently made from either metals (e.g.,stainless steel) or relatively durable plastics (e.g., polycarbonates).However, disposable food containers made from lower-cost plastics (e.g.,various polyethylenes, polyesters, and polypropylenes) are also used.

Regardless of whether reusable or disposable food storage containers areemployed, use of the containers typically involves generation ofsignificant quantities of waste. Disposable containers both precludecost savings that are realized with re-usable containers (since a newcontainer must be used each time) and generate solid waste which must bedisposed of properly. Although reusable containers avoid the economicwaste of single use containers, they require sanitation procedures thatare costly, time consuming, and generate significant quantities of(usually liquid) waste materials. Furthermore, sanitation of reusablefood containers tends to generate solid and liquid wastes (e.g., foodparticles, fats, and greases) that are not soluble in water and forwhich disposal in wastewater systems tends to be regulated. Thus,commercial scale sanitation of reusable food containers often requiresinvestment in equipment that isolates such wastes (e.g., grease traps),inspections to monitor compliance with applicable regulations, or both.In general, disposal of solid wastes (which are generally removed bytruck, rather than by cloggable pipes and sewers) is less regulated andmore flexible than disposal of liquid wastes containingnon-water-soluble components, in addition to conserving water used forwashing.

Others have proposed fitting disposable liners to food servicecontainers in order to alleviate the waste and inconvenience associatedwith cleaning reusable food service containers. Such liners can bedifficult to install and to remove in a sanitary fashion. Also, they aresusceptible to bypass if food products from the interior of the linerare spilled or migrate beneath the liner. When such liners are notadapted specifically to the food service container, problems of fittingand use arise from the unmatched dimensions of the liners andcontainers. For example, non-fitted liners can fold or crease to createpockets in which food products can accumulate or be hidden, leading tospoilage or bacterial growth that can contaminate food products in theremainder of the container. Fitted liners have the drawback that theyfit only a specific container, but not others. Inserted liners also havethe drawback that they tend to move or slide around in the food servicecontainer when foodstuffs are manipulated therein. Furthermore, knownliners also have disadvantages stemming from the fact that they areformed (like plastic bags) by welding, adhering, or otherwise sealingplastic sheets along a seam. The seams can often leak or tear, defeatingthe purpose of the liner. Insertable liners also tend to be relativelyunsightly and expensive.

There is a continuing need for a food container that can hygienicallycontain food and food service items and that can be rapidly andconveniently recycled for multiple uses, preferably without generationof excessive waste materials and while presenting a favorableappearance. The subject matter of the present disclosure addresses thisneed.

BRIEF SUMMARY OF THE DISCLOSURE

Various types of subject matter are described in this disclosure.

In prior related applications (U.S. patent applications No. 12/620,460,filed 17 Nov. 2009 and Ser. No. 11/734,285, filed 12 Apr. 2007, and U.S.provisional patent applications 60/794,409, filed 24 Apr. 2006 and60/855,597, filed 31 Oct. 2006), use of technology similar to thatdescribed herein was described in the context of making articles such aspaint trays for use in applying paint to a surface with a paint roller,and in particular to a paint tray having a one or more layers of apeelable surface film, whereby the paint tray can be cleaned after useby peeling away the upper film surface. Those applications also relatedto methods for converting multiple layers of material into a stack orroll and forming the paint tray or other container with adhered layers.It was recognized that those methods could lend themselves to a numberof markets other than paint trays, i.e., trash cans, buckets, metalpaint trays, cat litter containers, camping plates, medical trays, etc.

In one aspect, the subject matter described herein relates to apeelable, multi-use food service container. The container includes arelatively rigid sheet of a thermoformable polymer and at least one, andpreferably a plurality of, second sheets of a polymer, each second sheethaving a sanitary face and an adhesion face. A first surface of therigid sheet has a conformation adapted for holding, supporting, orcontaining a food service item. Each of the second sheets overlaps therigid sheet at the first surface and conforms to the shape of the firstsurface. Interposed between the rigid sheet and the adjacent secondsheet is a first barrier composition that adheres (e.g., peelably) therigid sheet and the adhesion face of the adjacent second sheet. A secondbarrier composition (identical to or different from the first) isinterposed between the adhesion and sanitary faces of adjacent secondsheets. The second barrier composition peelably adheres the secondsheets to one another. The container thus has one or a plurality ofhygienic second sheets peelably adhered to a surface adapted forholding, supporting, or containing a food service item. In oneembodiment, the second barrier composition is identical between allsecond sheets. In another embodiment, a second sheet more distal fromthe rigid sheet is more easily peeled from the second sheet underlyingit than is a second sheet more proximal to the rigid sheet. Thecontainer can have a protective coat layer applied atop the uppermostsecond sheet to prevent contamination of and physical damage to thesecond sheet(s), such as might occur during manufacture, storage,shipping, or installation of the container.

In another aspect, the disclosure relates to method of operating a foodstation. The method involves assembling one or more first food products(e.g., a sandwich or salad) from components stored in multiple foodcontainers, including at least one selected component that is held in apeelable food container described herein. After assembling first foodproduct(s) (for example, when the ingredients in the container aredepleted, at the end of a business day or shift, or after a pre-selectedperiod of time), a second sheet is peeled from the peelable foodcontainer (revealing a sanitary surface that can be contacted with freshfood components), and more of the selected component is added to thepeelable food container. One or more second food products (identical toor different from the first food products) are then assembled fromcomponents stored in the food containers, including at least theselected component.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a roll of stacked liner sheets and asubstrate sheet (master PAD roll) ready for thermoforming.

FIG. 2 is a sectional side view of a tray sheet section positionedbetween heaters prior to thermoforming.

FIG. 3 is a sectional side view of a heated tray sheet sectionpositioned in a thermoforming apparatus prior to thermoforming.

FIG. 4 is a sectional end view of a thermoformed tray system prior toejection from the thermoforming apparatus.

FIG. 5 is a detailed sectional side view of a segment of a stack ofliner sheets and a substrate sheet.

FIG. 6 is a top view of a preferred tray system.

FIG. 7 is a top view of an alternative preferred tray system.

FIG. 8 is a side view of an alternative tear tab assembly.

FIG. 9 is a side view of another alternative tear tab assembly.

FIG. 10 is a side view of yet another alternative tear tab assembly.

FIG. 11 is a side view of yet another tear tab assembly.

FIG. 12 is a side view of a pad of liner sheets.

FIG. 13 is a sectional side view of a stamping apparatus and a pad ofliner sheets.

FIG. 14 is a side view of a stack of substrate and sheets.

FIG. 15 is a sectional side view of a stack of substrate and sheets inpreparation for molding into a female cavity mold.

FIG. 16 is a sectional side view of a stack of substrate and sheetsmolded into a female cavity mold.

DETAILED DESCRIPTION

In this disclosure, terms such as horizontal, upright, vertical, above,below, beneath, and the like, are used solely for the purpose of clarityin illustrating the subject matter disclosed herein, and should not betaken as words of limitation. The drawings are for the purpose ofillustrating the subject matter disclosed herein and are not intended tobe to scale.

The subject matter of this disclosure relates to various embodiments.

Thermoformable Stack

In one embodiment, the subject matter of this disclosure relates to athermoformable stack. The stack includes a first sheet of athermoformable polymer and at least a second polymeric sheet (sometimesreferred to herein as a “liner” sheet) that overlaps the first sheet atan overlapping region. The first and second sheets can have the samecomposition and thickness, or these characteristics can be different.The stack can include multiple second polymeric sheets (made of the sameor different polymers and having the same or different thicknesses). Thestack can also include sheets of other materials, such as metal sheets.A layer of a first barrier composition is interposed between faces ofthe first and second sheets in at least a portion of the overlappingregion, preferably including substantially all of the first surface. Thefirst barrier composition prevents fusion of the surfaces of the firstand second sheets at the thermoforming condition. When the stack issubjected to the thermoforming condition, the first sheet assumes athermoformed shape, the shape of the second sheet conforms to the shapeof the first sheet, and the first and second sheets do not fuse in theportion of the overlapping region.

When the stack includes at least one pressure-deformable sheet, such asa metal sheet, as a first and/or second sheet, the stack can be shapedusing ordinary bending, stamping, and other pressure-based shapingmethods. Such stacks preferably include first and second sheets that canwithstand pressure, shear, deformation, and stretching forces inherentin pressure-based shaping methods without tearing or becoming punctured.By way of example, thin, stretchable nylon sheets can be adhered to analuminum sheet, with a first barrier composition interposed between thealuminum sheet and the adjacent nylon sheet and a second barriercomposition interposed between adjacent nylon sheets. Such analuminum/nylon stack can be subjected to a press that deforms thealuminum sheet into a desired shape, with the nylon sheets stretching tomatch the shape without becoming substantially de-adhered from thesurface of the aluminum sheet or from one another. In this manner,shaped metal objects having peelable polymeric layers can be made, ascan articles made from other pressure-deformable materials (e.g.,uncured ceramic pastes).

The second sheet is made of a material that is selected such that it iscapable of maintaining its structural integrity at a thermoformingcondition at which the first sheet can be thermoformed. The second sheetis capable of conforming to the shape of the first sheet as the firstsheet is thermoformed at the thermoforming condition. If desired, thesecond sheet can be a material that is also thermoformable at thethermoforming condition, but this is not a requirement. However, if anon-thermoformable second sheet is used, the second sheet may detach,deform, or pull away from the first sheet following thermoforming. Evenif the second sheet is thermoformable, these behaviors can nonethelessmanifest themselves if the first and second sheets are made of differentmaterials (owing, for example, to different coefficients of thermalexpansion). When the second sheet is a non-thermoformable material, thecharacteristics of the second sheet and any adhesive in the adjacentbarrier compositions should be selected to retain the desiredconfiguration of first and second sheets in the finished article. By wayof example, if one or more of the second sheets is an elastic material,then the elastic material should be selected such that it cantemporarily deformed at the thermoforming conditions, the adhesive(s)should be selected such that they will adherently oppose the tendency ofthe elastic material to resume its original shape after thermoforming,or some combination of these. An adhesive in the interposed barriercomposition can thereby cause a second sheet to remain conformed to theshape of the underlying thermoformed surface, even if the second sheetitself is not thermoset at the thermoforming temperature.

One or more tabs can be interposed between the first sheet and secondsheets. If a tab extends beyond an edge of either sheet, the tab can beused to facilitate separation of the first and second sheets afterthermoforming. The tab can be adhered to either sheet or to neither.

In one embodiment, the tab is relatively fixedly adhered to the secondsheet and either peelably adhered to or not adhered to the first sheet,such that the second sheet can be peeled from the first by grasping thetab and pulling the second sheet away from the first by way thereof.

In a second embodiment, the tab is relatively fixedly adhered to thefirst sheet and either peelably adhered to or not adhered to the secondsheet, such that the second sheet can be peeled from the first byscratching (e.g., with a fingernail or an edged instrument, such as thetine of a fork) the edge of the second sheet that overlies the tab tobegin partial peeling of the second sheet at the location of the tab,and then grasping the partially peeled portion of the second sheet andmanually peeling the remainder of the second sheet away from the firstby pulling on the partially peeled portion. In this second embodiment,if the second sheet is peelably adhered to the tab (i.e., rather thannot adhered at all to the tab), then adhesion of the second sheet to thetab can exclude materials (e.g., dust, liquids, or food particles) fromthe space between the tab and second sheet, rendering the tab surfaceclean upon peeling the second sheet therefrom. This can be of particularsignificance in applications (e.g., in food service containers) in whichpreservation of a sanitary surface upon peeling is desired.

Although a loose stack of polymeric sheets can be thermoformed using thematerials and methods described herein, it can be convenient to bind thefirst and second sheets to one another (and to bind multiple secondsheets together, where multiple second sheets are present) prior tothermoforming (e.g., to facilitate combination, storage, shipping,handling, manufacture, and alignment of the sheets). The means used tobind the sheets to one another is not critical, but preferably does notaffect the properties of the sheets in the region(s) of the sheets thatare to be thermoformed. By way of example, the sheets can be boundtogether using a glue applied to a common edge of the first and secondsheets, by fusion of a common edge of the first and second sheets, bystapling the first and second sheets together, by adhering the sheetstogether using an adhesive applied between the sheets at an inter-sheetarea distinct from the shaped section of the sheets, or by other means.

In order to prevent detachment or deformation of the second sheet awayfrom the first sheet after thermoforming, the first barrier compositioncan include an adhesive that peelably adheres the first and secondsheets. By incorporating such an adhesive into the first barriercomposition, thermoformed articles can be made in which the second sheetcan be peeled away from the first sheet, preferably (i.e., by judiciousselection of an adhesive) without tearing either of the first and secondsheets. All, or only a portion, of the overlapping region can be coatedwith the adhesive-containing first barrier composition. When a tab isinterposed between polymer sheets, the tab can be adhered to theadhesive and used to pull the edge of the sheet to which the tab isadhered away from the adjacent sheet to which the tab is not adhered. Inalternative configurations, the adhesive can be incorporated into thebarrier composition or the adhesive can be a composition discrete fromthe barrier compositions. By way of example, a barrier compositionhaving perforations or holes therethrough can be interposed betweensheets and a separate adhesive interposed between the sheets on one sideof the barrier composition (i.e., the adhesive contacting both sheetsthrough the holes or perforations), with the adhesive preventing fusionof the sheets, but adhering them where it is present and the barriercomposition preventing fusion of the sheets where the adhesive is notpresent.

An important embodiment of the subject matter disclosed herein is astack (sometimes referred to herein as a “master pad roll” when providedin the form of a rolled stack) of overlapping polymeric sheets. Thisstack includes the first sheet, which is a thermoformable polymer, andat least one, and preferably a plurality (e.g., 2, 3, 6, 10, or 20), ofsecond polymeric sheets. Each second sheet overlaps the first sheet atthe overlapping region, is capable of maintaining its structuralproperties (i.e., each sheet maintains its integrity and, preferably,its pliability and approximate thickness) at the thermoformingcondition, is capable of conforming to the shape of the first sheet asthe first sheet is thermoformed at the thermoforming condition, and hasa layer of a second barrier composition interposed between it and eachadjacent second sheet in a portion of the overlapping region. The firstbarrier composition prevents fusion of the surfaces of the first sheetand the adjacent second sheet at the thermoforming condition. The secondbarrier composition (which may be identical to the first) preventsfusion of the surfaces of adjacent second sheets at the thermoformingcondition. When the stack is subjected to the thermoforming condition,the first sheet assumes a thermoformed shape, the shape of each of thesecond sheets conforms to the shape of the first sheet, and the sheetsdo not fuse in the portion of the overlapping region. In thisembodiment, each of the second sheets can have different, identical, orsubstantially the same composition. Likewise, the compositions of thefirst sheet and any or all of the second sheets can be different,identical, or substantially the same.

As with the first barrier composition, the second barrier compositioncan include an adhesive (i.e., the same adhesive as the first or adifferent adhesive). Such a second barrier composition peelably adheresadjacent second sheets. An article made by thermoforming a stack of thissort will have multiple peelable layers. Such articles are desirablewhen, for example, a renewably clean and/or sanitary surface is requiredof an article, and particularly in situations in which cleaning of thesurface is difficult, time-consuming, distasteful, or hazardous. In oneembodiment, an article having a relatively thick (e.g., 10 to 40 mils)base (substrate) layer made from a thermoformed polymer can havemultiple thin (e.g., 1 to 7 mils) peelable layers that are separatelypeelably adhered to the base in a stacked configuration. The base canprovide shape and rigidity to the article (e.g., a paint tray, a toiletseat, or a food service container), and the peelable layers can providea renewably clean surface upon peeling of individual layers.

The stack described herein has at least one second sheet on at least oneface of the first sheet, as described above. Multiple second sheets canbe arranged on the first sheet, adjacent one another, at a distance fromone another, overlapping one another, or any combination of these. Thesecond sheets can be stacked atop one another, with the edges of thestacked second sheets coinciding perfectly or nearly perfectly with oneanother, with the edges of each stacked second sheet completely coveringone or more edges of the sheet over which it is stacked, with the edgesof each stacked sheet receded away from one or more edges of the sheetover which it is stacked, or any combination of these. Furthermore,second sheets can be arranged on one or both faces of the first sheet.On each face of the first sheet, there can be a single second sheet,multiple non-overlapping second sheets, multiple partially-overlappingsecond sheets, or multiple stacked second sheets.

When tabs are interposed between adjacent sheets, at least a portion ofthe tab should extend beyond an edge of one of the adjacent sheets, tofacilitate grasping of the tab, the edge of the sheet, or both. If anadhesive is interposed between the adjacent sheets, the tab canfacilitate peeling of the adjacent sheets, particularly if the adhesivecompletely fills the gap (i.e., all the way to the edges of the sheets)between the adjacent sheets. If no adhesive is interposed between theadjacent sheets, the tab can nonetheless facilitate separation of theadjacent sheets by relieving any pressure or electrostatic attraction inthe inter-sheet gap, by providing a region in which electrostatic forcesbetween the sheet surfaces are disrupted, or simply by providing amechanical lever by which expansion of the inter-sheet gap can beinitiated.

In an advantageous embodiment, tabs are interposed between sheets insuch a manner that the tabs between sheets alternate between one side ofthe shaped article (or stack) and the other side, for example so thatpeeling a sheet using a tab interposed between the top sheet and thenext (i.e., underlying) sheet on the right side of the shaped articleexposes a tab interposed between the next sheet and the third sheet onthe left side of the shaped article. (See, e.g., FIG. 11.) Particularlywhen stack materials are provided in rolled form, it can be advantageousto have the tabs arranged symmetrically along the sides of the rolls, sothat the rolled stack material has approximately the same size at bothends of the roll.

In one embodiment, tabs extend beyond the edges of both adjacent sheetsbetween which the tab is interposed. In this embodiment, the tab can begrasped independently of the sheets and used to initiate peeling. Whilethis embodiment has the advantages of ease of use and visibility, it hasthe disadvantages that the tabs can be unsightly and compromisesanitation (e.g., by providing a spot at which sheets can beinadvertently peeled and an otherwise-sanitary surface between thepeeled sheets can be exposed to environmental contaminants).

In another embodiment, the tab is fixedly adhered to one of two adjacentsheets and peelably adhered to the other sheet, which does notcompletely cover the tab. In this embodiment, the tab is not used as ahandle or grasping point for peeling either sheet to which it isattached. Instead, the tab provides a surface (e.g., a scratch-resistantsurface) from which a portion of the sheet that is peelably adheredthereto can be peeled by scratching, abrading, or picking the edge ofthat sheet at the tab surface. When a plurality of such tabs are used ina stack of sheets, the tabs can, for example, be arranged such that thetab for facilitating peeling of the uppermost (relative to the firstsheet) second sheet runs down the right of the stack, with the uppermostsecond sheet completely obscuring the tab for facilitating peeling ofthe underlying second sheet, which runs down the left of the stack. Uponpeeling of the uppermost sheet, the tab for facilitating peeling of theuppermost sheet will be completely exposed (i.e., because the portion ofthat tab that was partially obscured by the uppermost sheet prior topeeling will now be exposed), and the tab for facilitating peeling ofthe underlying second sheet will be partly exposed (part of that tabbeing obscured by that underlying second sheet, which can be peeledtherefrom in like manner as for the uppermost sheet). A similarside-to-side alternating arrangement can be used for multiple secondsheets, with the width of the sheets increasing with proximity to thefirst sheet (i.e., such that each second sheet completely obscures allbut one of the tabs underlying it and partially obscures that remainingtab (at which peeling of the sheet can be initiated).

In embodiments in which a tab is peelably adhered to and partiallycovered by an upper second sheet and relatively fixedly adhered to anunderlying (relative to the first sheet) second sheet, it can beconvenient to include on the tab indicia for indicating the operabilityof the tab. For instance, because the tab is partially covered by theupper sheet, the non-covered portion of the tab can be imprinted withthe first designation “̂̂̂̂ PEELHERE ̂̂̂̂”, with the upper portion of theletters adjacent the overlying edge of the upper sheet, to indicate theedge of the upper sheet which should be peeled from the tab. Theobscured portion of the tab can be imprinted with the second designation“vvvv DO NOT vvvv” immediately above the first, so that when the uppersheet has been peeled from the tab (i.e., when the tab is no longeruseful), the full indicium

-   -   “DO NOT    -   XXXX XXXX    -   PEEL HERE”

(i.e., a combination of the first and second designations) is visible.Other suitable indicia can be used.

The stack described herein can be prepared and provided in the form ofmulti-sheet leaves, folded bundles, or rolls, for example. In manypolymer-processing operations, rolls of polymeric materials arepreferred for ease of handling. Rolls of the stack described herein canbe prepared simply by winding the stack about itself, or about a coresuch as a paper or wooden tube or cylinder, in a rotary fashion. Inorder to minimize unintended interactions between the bottom of thestack in one layer of the roll and the top of the stack in an adjacentlayer of the roll, a release agent can be interposed between layers ofstack as it is rolled. In one embodiment, the release agent is a sheetof a material such as paper or waxed paper. In another embodiment, therelease agent is an oil or other liquid agent which inhibits or preventsirreversible interaction of stack layers. By way of example, a thin filmof a silicone-based compound (e.g., a liquid polysiloxane-containingcomposition, such as a silicone oil) can be applied to the top, bottom,or both top and bottom of the stack as it is rolled. The release agentshould either be an agent which does not affect thermoforming operationson the stack or an agent which can be separated from the stack prior tothermoforming operations.

Images, text, designs, or other printed matter can be included on one ormore of the sheets of the stack and articles made by thermoforming thestack. By way of example, label text and graphics can be printed on theoutermost second sheet (i.e., the second sheet on the “top” of thestack, having no other second sheets atop it). Such label informationcan be printed on the exterior of the sheet (i.e., on the surface of theproduct) or, if the outermost second sheet is not opaque, theinformation can be printed on the inner surface (i.e., first-sheet-side)of that sheet. Such printed matter should encapsulated between the sheetand the barrier composition that is interposed between the outermostsheet and the adjacent sheet. Encapsulation of the printed matter canensure that the printed matter is peeled off with the outermost sheet(i.e., does not adhere to the adjacent sheet) when the outermost sheetis peeled away from the adjacent sheet. Printed matter can be applied tothe inner and/or outer faces of any of the sheets described herein inthe same manner. Judicious selection of surface treatments (e.g., Coronatreatment) and adjacent adhesives can ensure that the printed matterremains bound to a desired surface when the adjacent adhesive (and anypolymeric or other sheet adhered to the desired surface by the adhesive)is peeled away.

When printed matter is included on a surface of the shaped articlesdescribed herein, the precise materials and methods used to print thematter on the surface are not critical, other than that they should beselected such that the printed matter will remain attached to thesurface to which it is applied during normal use of the shaped article(unless detachment of the printed matter is considered acceptable). Byway of example, in one embodiment of the thermoformed,multiple-peelable-layer paint tray disclosed herein, the outermostpeelable layer is transparent and the printed matter is applied to theunderside of that layer (i.e., the face of the layer that is adhered tothe underlying surface) such that an adhesive in the barrier compositionbetween that layer and the underlying surface adheres to the printedmatter (and thence to the outermost layer) when the outermost layer ispeeled away from the underlying surface. In another embodiment, thepenultimate peelable layer (i.e., the second sheet adjacent the firstsheet) is transparent and the printed matter (e.g., text reading, “Thisis the final peelable layer!”) is applied to the underside of that layer(i.e., the face of the layer that is adhered to the surface of the firstsheet) such that the printed matter is removed, together with anyadhesive present in the first barrier composition, when the penultimatepeelable layer is peeled away from the first sheet.

Included in embodiments of this disclosure are shaped articles thatinclude multiple, substantially identically-shaped sheets ofthermoformable polymers that overlap at an overlapping region.Interposed between each pair of sheets, in at least a portion of theoverlapping region, is a layer of a barrier composition. Because thebarrier composition prevents the sheets from fusing across their entirefaces (i.e., the sheets do not fuse at the portions of the overlappingregion at which the barrier composition is present when the sheets arethermoformed) the article is separable into multiple, substantiallyidentically-shaped subarticles upon separation of the sheets. Thebarrier composition can be omitted from at least a portion of the gap atthe overlapping portion of the sheets in order to form an article inwhich the substantially identically-shaped subarticles remain boundtogether at the overlapping portion that lacked the barrier compositionduring thermoforming. Alternatively, that portion of the gap can befilled with an adhesive to (reversibly or irreversibly) bind theoverlapping portions corresponding to the sub-articles. Such bundles ofsubarticles can often be stored, shipped, handled, manufactured, andused more conveniently and more energy-efficiently than an equivalentnumber of separate subarticles, and the subarticles can be separatedfrom one another at a convenient time and place simply by breaking,cutting, or otherwise separating individual articles from the boundoverlapping portion. Such an article can include multiple (e.g., 2, 6,10, or 20) discrete egg cartons, cookie trays, cups, blister packs,computer keyboard covers, food containers, or paint tray liners that canbe separated from one another as desired. The multiple items can havesubstantially the same thickness, different thicknesses, or acombination thereof.

The subject matter described in this disclosure includes a shapedarticle that includes a shaped thermoformable polymer sheet, a pluralityof second polymer sheets, and first and second barrier compositions. Thesecond sheets overlap the thermoformable sheet at an overlapping regionand conform to the shape of the thermoformable sheet at substantiallythe entire overlapping region. The first barrier composition isinterposed between and peelably adheres the thermoformable sheet and theadjacent second sheet. The second barrier composition is interposedbetween and peelably adheres adjacent second sheets. In an article ofthis type, the second sheets are peelably removable from the article.The article can include tabs interposed between adjacent second sheetsand a tab between the thermoformable sheet and the adjacent secondsheet. By way of example, the shaped article can be a paint tray havingpeelable liner layers, as described herein. Further by way of example,the shaped article can be a food service container, as described herein.

Further details of the materials and methods suitable for use in thearticles, methods, and compositions described herein are provided in theensuing sections of this disclosure.

Thermoformable Polymer Sheets

The identity and composition of thermoformable polymer sheets used inthe articles and methods described herein are not critical. A skilledartisan will recognize that substantially any thermoformable polymericmaterial can be used. Examples of suitable thermoformable polymericmaterials include polyethylene terephthalates, polyesters, polyethylenes(including high density polyethylenes and high molecular weightpolyethylenes), polypropylenes, polyvinylchlorides, polystyrenes,nylons, copolymers of these, and combinations of these.

A skilled artisan can select a thermoformable polymeric material, orcombinations of such materials, suitable for use in substantially anyapplication by considering such properties as the shrink rate,crystallinity, heat deflection temperature, tear strength, draw ratio,thickness, rigidity, melt temperature, thermal conductivity, heatcapacity, and polymer backbone orientation of the material(s). Selectionof materials can also be guided by properties that do not necessarilydirectly impact the thermformability of the materials, such as cost,color, opacity, recycled material content, environmental impact, surfaceenergy, chemical resistance, and surface sheen of the materials.

In selecting appropriate materials, an artisan should consider at leasttwo sets of conditions: the environmental conditions to which thefinished, shaped article will be subjected (e.g., during transportation,storage, and use) and the conditions that the materials will experienceduring the thermoforming process. Materials should be selected so as toexhibit the desired color, shape, strength, rigidity, and peelability,for example, once the materials have been shaped in the thermoformingprocess into their final, desired form. The materials should also beselected, together with the thermoforming conditions, so as to allowassembly and shaping of the materials into their final, desired formusing thermoforming conditions available to the artisan.

Peelable Polymer Sheets

The identity and composition of peelable polymer sheets used in thearticles and methods described herein are not critical. A skilledartisan will recognize that substantially any peelable polymericmaterial can be used.

In some embodiments, peelable sheets preferably have sufficientstructural integrity that they do not tear or significantly stretch whensubjected to forces necessary to peel them from surfaces to which theyare adhered with a peelable adhesive. For example, when a paint trayhaving peelable surface layers is made as described herein, each of thepeelable surface layers can preferably be peeled from the underlyingsurface as a single, integral sheet (i.e., no holes or tears) whilecontaining paint coating its non-adhered surface. Peelable sheets thattear, stretch, or puncture are acceptable in embodiments in whichcontainment of liquid within the peelable sheet is not required. Forfood service containers, as described herein, the maker should considerthe characteristics of the peelable sheets at the temperature at whichthe sheets are likely to be peeled (e.g., either room temperature or ahigher or lower temperature used, respectively, for storing heated orcooled foods).

The peelable sheets are preferably thin (e.g., 1 to 4 mils, preferably1-2 mils thick) and highly flexible. Sheets having a thickness in excessof 8 mils can be difficult to peel, and so sheets thicker than 8 milsare not preferred. The peelable sheets can be made from substantiallyany polymeric material(s) and by substantially any sheet-formingprocess. By way of example, suitable polymer sheets can be made byblowing, molding, casting, or extruding suitable polymer materials, orby some combination of these processes. When made of thermoformablematerials, the peelable sheets are preferably thermoformedsimultaneously with the substrate sheet of thermoformable material towhich they are adhered. When made of non-thermoformable materials, thepeelable sheets should be capable of maintaining their structuralintegrity at a thermoforming conditions at which the substrate sheet towhich they are adhered is thermoformable. Examples of suitable polymersfor peelable sheets include polyethylenes, polypropylenes, polyethyleneterephthalates, nylons, polyvinyl chlorides, copolymers of these, andcombinations of these.

Peelable sheets can be selected to be rigid (i.e., retain their shapeafter peeling, e.g., akin to prior art molded paint tray liners that canbe lifted out of a paint tray and retain their shape when subjected tosmall forces) or substantially non-rigid (e.g., blown polymeric sheetssuch as the material used in trash can liners and trash bags).

The peelable nature of an individual peelable sheet can derive fromsurface attraction between the peelable sheet and the surface underlyingit. Preferably, however, an adhesive is interposed between the sheet andthe surface (e.g., in the barrier composition) and the peelable natureof the sheet derives primarily from the adhesive forces exerted by theadhesive upon the sheet and the surface. An adhesive can be selected(e.g., based on the chemical identity or the surface treatment of thepeelable sheet or the surface to which it is adhered) so that, uponpeeling of the peelable sheet, the adhesive preferentially remainsadhered to the peelable sheet, or to the surface. For instance, when thefunction of the peelable sheet is to expose the surface free of adhesiveand other contaminants, the adhesive can be selected so that it bothadheres the peelable sheet and the surface and adheres more strongly(i.e., more tenaciously) to the peelable sheet so that, upon peeling,the adhesive is removed from the surface along with the peelable sheet.

Differences in the tenacity with which an adhesive binds the opposedsurfaces of two polymer sheets can be controlled in a number of ways,including by coating one or more portions of one surface with acomposition that inhibits binding of the adhesive to the surface.Preferably, however, differences in the tenacity of adhesive-binding arecontrolled by selecting or treating the polymer sheets such that theiropposed surfaces exhibit a difference in surface energies. If thedifference between the surface energies of the two surfaces isrelatively large—at least 5 Dynes—then the adhesive will bindsignificantly more tenaciously to one surface than the other. As thedifference in surface energies of the two surfaces increases beyond 5Dynes, the likelihood that all of the adhesive will remain with onesheet when the two sheets are separated increases. A difference of 5 to14 Dynes between the adhered surfaces of the two sheets is consideredappropriate.

It may be possible to separate two surfaces having an adhesiveinterposed between them, even if the surface energies of the surfacesdiffer by less than 5 Dynes. In this situation, the adhesive may adhereto each of the two surfaces with roughly equal tenacity, meaning thatthe adhesive may adhere to both surfaces (at various portions) after thetwo surfaces are separated from one another. In many applications, it isdesirable to have most or all of the adhesive to adhere to the surfaceof only a single one of the polymer sheets (usually the one being peeledaway from the remaining sheets or substrate). For such applications, thetwo surfaces contacted by the adhesive should preferably have surfaceenergies that differ by at least about 5 Dynes.

The amount of force needed to separate peelable sheets from theirunderlying surface is not critical, but is preferably sufficiently smallto prevent tearing and substantial stretching of the peelable sheet uponmanual peeling of the sheet from the surface. The amount of separationforce needed is a function of the materials selected for the peelablesheets, the underlying surface, and any barrier composition or adhesiveinterposed between them. Practically speaking, the tenacity of adhesionbetween a peelable sheet and the underlying surface should be selectedso that the sheet can be peeled away from the surface using normal humanstrength, but not so tenacious that the sheet must be torn or puncturedby a person peeling the sheet from the surface. A skilled artisanrecognizes that the numerous variables (e.g., the angle at which thesheet is pulled from the surface, whether fingernails are applied to thesheet surface, the speed with which the sheet is peeled, the temperatureof the shaped article at the time of peeling) can affect the peelingcharacteristics of the sheet, and the materials described herein includeall materials that are operable under the ambient conditionscorresponding to anticipated uses of the materials and shaped articles.

To the extent that an objective measure of the force needed to peel asheet from an underlying substrate surface is desired, a standardizedtest of peel strength can be used. An example of a suitable test is ASTMD3330/D3330M, which is a standardized test for peel adhesion ofpressure-sensitive tape. A modification of this procedure (e.g.,substituting a sheet of the substrate material in place of the standardsteel sheet in ASTM D3330/D3330M and selecting a peel angle appropriatefor the intended use of the shaped article being tested) can also beused. In each case, the characteristics of the shaped article or stackshould be selected such that the peel strength of the finished articleis within the limits of human strength.

Various surface treatments and polymer sheet ingredients can be used toaffect the surface energy

In one embodiment of the stack and shaped articles described herein,multiple adjacent polymer sheets are made of the same material. Unlesstreated non-identically, the two faces of a polymer sheet will normallyhave the same surface energy. Therefore, in stacks and articles whichinclude multiple identical polymer sheets, it is important that the twofaces of the identical polymer sheets (e.g., the adhesion and sanitaryfaces of second sheets of food service containers described herein) betreated differently, so as to yield a polymer sheet having differentsurface energy values for each of its two faces. Such sheets arepreferably treated such that the surface energies of their faces differby 5 Dynes or more. Many compositions and methods for affecting thesurface energy of polymer sheets are known to skilled artisans in thisfield, and substantially any of those methods may be employed. Suchmethods include conventional surface finishing techniques such asgrinding and polishing, annealing processes, Corona treatment, andplasma contact techniques such as atmospheric, chemical, and flameplasma techniques. Compositions for affecting the surface energy of asurface of a polymer sheet are also well known, and include compoundsthat can be contacted or reacted with the surface to modify its chemicalor physical properties (affecting its surface energy).

An example of a suitable surface treatment is the process known asCorona treatment or Corona discharge treatment, which involvesapplication to a surface of a high-frequency, high voltage electricaldischarge. Corona treatment raises the surface energy of a polymericsurface. Applied to one face of a polymer sheet having two otherwiseidentical faces, Corona treatment will raise the surface energy of theface, relative to the opposite face of the sheet. The power applied in aCorona treatment can be controlled to limit the treatment substantiallyto one side of a sheet. At very high power, the treatment can raise thesurface energy of both faces of the same sheet which, in the absence ofother surface treatments, will not yield a polymer sheet havingdifferent surface energies on its two faces. If a polymer sheet isCorona treated at or near the time it is formed, the surfaceenergy-raising effects of the treatment can endure for weeks, months, oryears. If the sheet is Corona treated days, weeks, or later after thesheet is made, the surface energy-raising effects of the treatment canbe more transitory (e.g., enduring only for days or weeks). Polymersheets that are Corona treated at or very near the time they are formedcan be used in the stacks and articles described herein. Polymer sheetscan also be “bump-treated” (i.e., be Corona treated regardless of howlong it has been since the sheet was formed) shortly before making thestacks and articles described herein.

Peelable sheets can be made from clear, translucent, or coloredmaterials, ingredients and method for imparting each of thesecharacteristics being known in the art. Colorants and opacity agentsshould be selected in view of the intended use of the container. By wayof example, non-toxic, and preferably substantially non-leaching, agentsshould be used in food service containers as described herein. Where ashaped article is desired to have a selected color, that can be achievedby making the peelable sheets that color, or by making the rigid sheetsthat color and the peelable sheets clear or substantially transparent.

Barrier Compositions

The identity and composition of barrier compositions interposed betweenpolymer sheets used in the articles and methods described herein are notcritical. A skilled artisan will recognize that substantially anymaterial can be used as a barrier composition between two polymers, solong as it substantially prevents fusion of two polymers underconditions at which at least one of the polymers can be thermoformed. Awide variety of such compositions are known for this purpose.

Examples of suitable barrier compositions include adhesives (e.g.,peelable adhesives such as pressure-sensitive adhesives), known polymerrelease agents, a polymeric or paper film interposed between polymerlayers, and various liquids, including low-viscosity silicone oils.

A composition interposed between two surfaces (e.g., between the firstand second polymer sheets, or between two second polymer sheets, asdescribed herein) can act as a barrier composition between the twosurfaces if the composition coats at least one of the two surfaces at athermoforming condition, thereby preventing surface-to-surface contactand fusion of the two surfaces at the thermoforming condition.

A barrier composition prevents fusion of opposed polymeric surfaces onlywhen it is interposed between the surfaces at the thermoformingcondition. For that reason, the barrier composition must be interposedbetween the surfaces over the entire area for which fusion between thesurfaces is not desired. This can be achieved in various ways, includinguse of liquid and solid barrier compositions. When a stack is to bethermoformed to make a plurality of shaped objects that are not fusedover some portions, but fused at at least one portion (e.g., a stack ofcookie trays fused only at a single, frangible extension of the trays atone corner), the barrier composition is interposed among the polymersheets in the non-fused areas, but is not interposed between the polymersheets in the area in which fusion is desired. Multiple barriercompositions can be interposed between different portions of a pair ofsheet such that, together, the barrier compositions cover at least onesurface of the two sheets at every overlapping portion and preventfusion between the two sheets. If desired, certain portions can be leftuncovered by barrier compositions, such that those portions fuse oradhere to one another upon thermoforming (e.g., if peeled sheets are toremain attached to the surface from which they are peeled).

Liquid barrier compositions should be selected such that they completelycoat (i.e., wet) at least one of the surfaces over the entire area forwhich fusion is not desired. This can be achieved by selecting a liquidbarrier composition (i.e., a composition that is a liquid at at leastthe thermoforming condition, regardless of whether it is a liquid atwhich it is contacted with the surface) that has a surface tensionsignificantly greater (i.e., at least 2 Dynes, and preferably at least10 Dynes greater) than the surface energy of the surface with which itis contacted. This surface energy difference should ensure that theliquid barrier composition completely wets (i.e., coats) the area of thesurface for which fusion is not desired. Preferably, the liquid barriercomposition has a surface tension significantly greater than the surfaceenergy of both surfaces, so that the liquid is not displaced frombetween the surfaces at points at which the two surfaces are urgedtightly against one another.

Solid barrier compositions (e.g., polymer sheets) should be selected sothat the solid covers the entire area for which fusion is not desired.The identity of the solid is not critical, so long as it does notprevent the portions of a polymer sheet that are to be thermoformed fromreaching the thermoforming condition. Solid barrier compositions canprevent fusion of the surfaces (and/or) fail to fuse to one or bothsurfaces for a variety of reasons, any of which are sufficient to rendera material suitable as a solid barrier composition. Some solids can bepredicted to act as suitable barrier compositions, while other mayrequire empirical testing (e.g., thermoforming two sheets of the polymerwith the solid interposed between them) in order to determine theirsuitability. Either way, selection of an appropriate solid barriercomposition is within the ken of a skilled artisan in this field.

Another type of barrier composition that can be used is a compositionincorporated as an additive into one or both of the polymer sheets.These compositions melt and “bloom” to the surface of a polymer whenheated, pressed, stretched, or otherwise manipulated. If such acomposition is included in one or both of the polymer sheets such thatthe composition blooms at the surface of at least one sheet at thethermoforming condition and prevents contact between the polymer sheetsthemselves, then the composition can be used as a barrier composition inthe articles and methods described herein. A wide variety ofcompositions that exhibit such blooming behavior are known in the art.

Adhesives

The identity and composition of adhesive interposed between polymersheets used in the articles and methods described herein are notcritical. A skilled artisan will recognize that substantially anymaterial can be used as an adhesive between two polymers, so long as itreversibly binds the two polymer layers (at least when peelability ofthe two sheets is desired) and requires no more force to separate thepolymer layers than can be practically applied to the polymer layers bya person of ordinary strength. A wide variety of such compositions areknown for this purpose.

The adhesives used between a peelable polymer sheet and an underlyingsurface are preferably peelable, meaning that the polymer sheet can bepeeled from the surface by a person of ordinary strength, preferablywithout tearing or substantially stretching the sheet. Preferably, anadhesive having a coat weight of roughly 0.6 to 15 ounces per inch isused to adhere a peelable sheet to an underlying surface. A skilledartisan in this field is able to select a standard coat weight for agiven adhesive, empirically determine an appropriate coat weight, orboth. Thus, selection of an appropriate amount of adhesive is wellwithin the ken of an ordinarily-skilled artisan in this field.

A wide variety of suitable adhesives are known in the art and can beused as described herein. Pressure-sensitive adhesives are among thesuitable adhesives that can be used. Likewise, adhesives that adherepreferentially to one of two adhered surfaces, upon peeling of one ofthe surfaces away from the other) are suitable and are preferred incertain embodiments. By way of example, if an adhesive adheres morestrongly to a peelable polymer sheet than to a surface to which thesheet is adhered by the adhesive, the adhesive will tend to remain withthe sheet when it is peeled from the surface.

Various compounds and surface treatments can be used to reduce the forceneeded to pull an adhesive from a surface, and such compounds andtreatments can be used to modulate adhesion of an adhesive to a surfacedescribed herein.

Specific examples of adhesives that can be used in the articlesdescribed herein include polysiloxane-based adhesives, rubber cement,and acrylic adhesives (e.g., waterborne pressure-sensitive, acrylicadhesives of the MULTI-LOK™ brand family of acrylic adhesivesmanufactured by National Adhesives of Bridgewater, N.J.).

Printing

Text, images, or other graphical material can be printed onto one ormore faces of one or more of the polymer sheets described herein. A widevariety of materials and methods can be used to print such material ontothe surface of a polymer sheet. A difficulty inherent in printing onpolymer materials is that the printed matter can often easily bedisplaced from the polymer surface by heat, light, or mechanicalabrasion, leading to reduced print quality. Furthermore, it can beundesirable for the materials used for printing to contact materialsthat will be in contact with the polymer. For example, it can beundesirable to have printing inks contact paint on the interior surfaceof a paint tray or food on the interior surface of a food servicecontainer. These effects can be avoided by applying a clear polymersheet or layer over top of the printed matter, thereby securing it inplace and preventing its displacement. However, the clear layer oftencannot be peeled off without severely damaging the printed matter and/orleaving portions of the printed matter on the peeled sheet and theunderlying surface.

In one embodiment of the stacks and shaped articles described herein,printed matter is incorporated between polymer sheets and is peelablecoherently with one sheet. In this embodiment, the printed matter isprinted (preferably “reverse” printed, in that the printed matter isintended to be viewed through the sheet, rather than by viewing theprinted surface of the sheet) onto the face of a clear (or at leasttranslucent or not-completely-opaque) polymer sheet, and that face ofthe clear sheet is adhered to an underlying sheet. The tenacity withwhich the printed matter clings to the clear sheet and the tenacity towhich adhesive overlying the printed matter clings to the printed matter(and thence to the clear sheet) is greater than the tenacity with whichthe adhesive overlying the printed matter adheres to the underlyingsheet. Thus, when the clear sheet is peeled away from the underlyingsheet, the printed matter (and the adhesive overlying it) come away withthe clear sheet, leaving the underlying surface free of adhesive and/orprinted matter.

The tenacity of binding of printed matter to a polymer sheet can, asdescribed herein for adhesives, be affected by surface treatment of thepolymer sheet prior to printing upon it. Corona treatment and plasmadischarge techniques, for example, can raise the surface energy of apolymer surface, rendering it susceptible to more tenacious binding bythe printed matter. Likewise, surface treatment (e.g., Corona treatment)of a polymer surface having printed matter thereon can raise the surfaceenergy of the surface (including the portion on which the printed matterappears). By applying to the printed portion of the surface an adhesivethat adheres more tenaciously to the printed portion than to the opposedunderlying surface, adhesion of the adhesive with the printed matter canbe maintained upon peeling of the sheet carrying the printed matter fromthe underlying surface.

In another embodiment, a release agent can be interposed betweenadhesive contacting a sheet having printed matter carried thereon and anopposed surface. The release agent overlies the printed matter andprevents (or weakens) binding between the adhesive that contacts thatprinted matter and the portion of the opposed surface that is adjacentthe printed matter on the sheet. When the sheet is peeled from thesurface, the poor (or lack of) adhesion between the sheet and thesurface in the region where the printed matter occurs prevents damage tothe printed matter, which is peeled off with the sheet.

Thermoforming Apparatus and Conditions

The articles described herein can be made using known thermoformingapparatus and conditions. Of course, the apparatus and conditions shouldbe selected based on the identity and the characteristics of thematerials to be processed. Selection of appropriate thermoformingconditions, based on the identity(ies) of the materials to be processedis within the ken of a skilled artisan in this field.

Paint Trays and Other Thermoformed Articles

In one embodiment, the subject matter disclosed herein includes a painttray with a plurality of peelable liners that are simultaneouslythermoformed with the tray, with the liners being thermoformed to theshape of the tray interior surface at the same time the tray is formed.As used herein, the term “thermoformed” is intended to encompass variousmethods of shaping a thermoplastic sheet or stacked sheets by heatingthe sheet and applying a pressure differential to the opposed side ofthe sheet to conform the sheet to the shape of a mold surface.

While the subject matter of this disclosure is occasionally described interms of the preferred embodiment of simultaneously thermoforming asubstrate and a plurality of liner sheets or simultaneouslythermoforming a plurality of similar thin wall substrates with a releaseagent/barrier on the inner or bottom surface, it will be understoodafter reading the disclosure that the subject matter also includessimultaneously forming a substrate and a single liner sheet, and shapingthe liner sheets and substrate by other means, e.g., by stamping,injection molding or blow molding. The substrate, while preferably athermoformable plastic, may also be of other materials, e.g., metals.

In one example of thermoforming known as vacuum molding, a sheet ispositioned adjacent a female (or male) mold section and a vacuum isapplied to draw the sheet against the mold surface. A male mold sectionmay be pressed against the sheet on the opposite side of the sheet fromthe female mold section to assist in conforming the sheet to the shapeof the female mold section. In other processes, such as pressureforming, the heated sheet is pressed against a male mold section (or,more frequently, into a female mold section), usually with theassistance of a vacuum to conform the sheet to the mold shape.

In a preferred embodiment of the subject matter disclosed herein, atleast one, and preferably a plurality of stacked planar sheets of thinplastic serving as disposable liners (“liner sheets”) are positioned ona surface of a planar substrate sheet of a greater thickness to beformed into a paint tray or other shaped article (e.g., a food servicecontainer). The combination of liner sheets and a single substrate makesa “stack” (as disclosed elsewhere herein) or “tray sheet” when the stackis used for making trays. The liner sheets will preferably besignificantly thinner than the substrate sheet, e.g., the liner sheetsmay be from about 1 mil to about 6 mils thick, while the substrate sheetmay be from about 10 mils to about 40 mils thick.

Each liner sheet has an adhesive on its inner or bottom surface tosecure the liner sheets to the immediately adjacent sheet, with theinnermost or bottom liner sheet being adhered to the top surface of thesubstrate sheet. Preferably, the adhesive backing is a uniform coatingof adhesive over the entire inner surface of the sheets except wheretear tabs are located. While applying the adhesive in making the linersheets, the tabs can be added in line, anywhere in part or whole aroundthe perimeter of where the tray will be formed. This can be done bydeadening the adhesive. Tabs are applied to each liner sheet tofacilitate separation of the sheets. Suitable adhesives will be apparentto one skilled in the art, the requirement being that the adhesive is apeelable adhesive, i.e., an adhesive that will permit separation of oneliner sheet from another liner sheet or the substrate without tearingthe liner sheet.

The tray sheets can be shipped in either sheet form or roll form. Forconvenience in shipping, storage, and thermoforming, the tray sheet maybe provided to the thermoformer in a continuous roll form (“master padroll”). The roll can be continuously fed through the thermoformer, witheach length of tray sheet being indexed, then thermoformed into a shape,i.e., paint tray. The roll length and width can be as desired. Forexample, the master pad roll can be 5″ to 48″ in width. As anotherexample, the master pad roll can be 60″ in width.

The combined stack of sheets (i.e., stack or tray sheets), isthermoformed as a unit into the shape of the desired product, e.g., apaint tray with the liner sheets being on the interior of the painttray. Upon cooling, the tray sheet maintains its thermoformedconfiguration due to the thickness of the substrate sheet, while theconfiguration of the liner sheets is assisted by the presence of theadhesive backing.

The paint tray is used like one would use an ordinary paint tray thatdoes not have a liner. However, unlike the prior art trays describedabove, there is no need to place a preformed liner into the tray orattempt to hand shape a sheet of thin plastic to conform to the trayinterior. After use, the upper liner sheet can be simply peeled awayalong with the paint residue, exposing the next liner sheet as a cleanpaint tray ready for use.

The mold, and thereby the thermoformed tray system, can be of variousshapes. Generally, the resultant tray will have an open-top interiorcavity with a floor and continuous side walls. The paint tray mayinclude at least one paint well and a flat section, normally ridged, forremoval of excess paint from a roller dipped into paint within the paintwell. In a preferred embodiment, the improved tray may be comprised oftwo paint wells divided by a horizontal, flat central section so thatpaint can be placed in both wells. The flat section is connected toopposed ramps tapering upwardly from the paint wells.

In another embodiment of the subject matter disclosed herein, multiplecontainers such as plastic egg cartons, cookie trays, dessert gelatincontainers, blister packs, rigid paint tray liners etc., are produced bysimultaneously thermoforming multiple layers of plastic sheets havingthe same thickness. Sheets used in this application are generally fromabout 0.006″ to about 0.025″ thick. Preferably, a stack of sheets, e.g.,from 4 to 6 sheets, are provided to the thermoformer in roll form. Arelease agent, e.g., a coating, adhesive barrier or release film isapplied between the sheets to prevent the sheets from melting/bondingtogether during the thermoforming process, and to allow the finishedcontainers to be separated easily (e.g., a form of silicone may beintroduced between the layers of sheets. A zone coat of adhesive (e.g.,1 inch wide) may be applied along the edge of the substrate to allow foreasier transport of the rolls of substrates and sheets by keeping thematerial together in roll form more effectively. Stacks of sheets arethermoformed by being drawn or pressed into a mold having the desiredcavity shape.

Descriptions of Embodiments Illustrated in the Drawings

As illustrated in FIGS. 1 and 5, tray sheet 10, comprised of a pluralityof liner sheets 12 and a bottom substrate sheet 14, is shipped to thethermoformer as a roll 16.

As illustrated in FIG. 2, tray sheet 10 is pulled via the thermoformingmachine from roll 16 and positioned within a thermoforming apparatuscomprised of upper and lower heaters 22 and 23 to heat the sheet to amoldable state. While both ovens can be heated simultaneously, they alsomay need to be adjusted independently of one another. The heated sheetis then pulled further to a position over a vacuum source 24 asillustrated in FIG. 3. A female mold 26 conforming to the desired shapeof the tray system is positioned in communication with vacuum source 24.Heated sheet segment 10 is lowered onto mold 26 and a vacuum is drawn onmold 26 with vacuum source 24, shaping sheet segment 10 to the interiorcontours of mold 26 as shown in FIG. 4. The molded tray system is thencooled and ejected from mold 26, and edge trimmed if desired.

The resultant product is a thermoformed tray system comprised of asubstrate sheet in the shape of the desired tray, with a plurality ofliner sheets stacked thereon and held in place by adhesive layers, bothnatural or man made, between the liner sheets and the lowermost linersheet and the upper surface of the substrate sheet. All sheets aremolded into the shape of the desired tray.

A preferred paint tray 30 is illustrated in FIG. 6. Tray 30 is comprisedpreferably of a horizontal, flat central shelf 32 with ridges 34 toremove excess paint from a paint roller rolled across shelf 32, downramps 40 and paint wells 36 and 38 on opposite sides of ramps 40. Teartab 42 can be located anywhere on the perimeter of all liner sheets, orall or part of the entire perimeter of the liner sheet can form a tab 43for use in separating the liners. An alternative tray configuration isillustrated in FIG. 7, showing the addition of feet 44 for addedstability.

Various other means may be used to include tabs to facilitate separationof the tapes. For example, as shown in FIG. 8, the layers of linersheets 50 may be stepped during the converting process where thesubstrate 52 and liner sheets 50 are formed into a roll. The resultinglook will be like steps 54 on the edges, allowing the consumer to seethe edges of all the layers.

In another alternative shown in FIG. 9, the liner sheets 60 may be“strip coated” before it is made into the roll form. That is, adhesiveis applied to the body of the liner sheets 60, except for the area ofthe tabs 62. Thus, the liner sheets 60 have adhesive except for theedges (e.g., ½″), either on one side or both sides of the liner sheets.The end result is the edges of the paint tray will have no adhesive onthe “tabs” 62, allowing the consumer to identify and begin peeling thelayers.

Yet another alternative as shown in FIG. 10, is to use actual separatetabs 70 on the edges of the liner sheets 72 to distinguish betweenlayers. The separate tabs 70 could be tape/film of plastic or paper(e.g. ¾″ wide, with or without adhesive) to be applied on the ends ofthe protective tape on either the top or bottom preferably the bottom(this side of the protective tape has the adhesive). This tape/filmcould be of various colors and designs and will serve as an aid for theconsumer to pull apart the layers of liner sheets 72.

Yet another alternative is shown in FIG. 11, using actual separate tabs56 on the edges of the liner sheets 66 to distinguish between layers,however tabs 56 are applied on opposing edges of sequencing liner sheets66, while liner sheets 66 are shifted, creating a pitter patter effectwith tabs 56 hidden underneath top liner sheets 66 until top layer isremoved. The separate tabs 56 could be tape/film of plastic or paper(e.g. ¾″ wide, with or without adhesive) to be applied on the ends ofthe protective tape on either the top or bottom, preferably the bottom(this side of the protective tape has the adhesive). This tape/filmcould be of various colors and designs and will serve as an aid for theconsumer to pull apart the layers of liner sheets 66.

While the subject matter disclosed in this section is describedprimarily in terms of the manufacture of a paint tray with a stack ofthermoformed sheet liners conforming to the interior dimensions of thepaint tray, it will be apparent that the broad concept of the subjectmatter disclosed herein can be modified for other applications. Forexample, as illustrated in FIGS. 12 and 13, instead of simultaneouslyshaping the substrate that forms the tray or other product and the linersheets, the substrate can be initially formed into the tray, or the traycan be otherwise manufactured. A pad of liner sheets 80 can then beformed within the tray. That is, a mold of the image of the product,e.g., paint tray 82, is suspended above the product (e.g., paint tray inplastic or metal) and sandwiched in between is a continuous roll ofliner sheets 80. The paint tray will be moving along a conveyor 84 andwhen the paint tray is nested opposing the mold image of the product 86,the two parts are “stamped” together, thus creating the finished productwith the pads of liner sheets.

In another alternative illustrated in FIGS. 14-16, multiple layers ofplastic sheets 90 having the same thickness, instead of liner sheets,can be thermoformed simultaneously, in order to make multiple products.Applications for this would include various containers such as plasticegg cartons, cookie trays, dessert gelatin containers, computer keyboardcovers, blister packs, (non-peelable) food service containers, rigidpaint tray liners etc. The multiple plastic sheets that can be used areanalogous to the substrate (i.e., relatively rigid) material used in thepeelable articles described herein, rather than the liner sheets whichare more stretchable and pliable (i.e., like a garbage bag) butgenerally unable to retain their shape under the influence of gravityunless adhered to a more rigid body such as the substrate. That is, theplastic sheets 90 that can be used in this process can be of a lesserthickness than the paint tray (i.e., they can be less than 30 milsthick), but they are generally not as thin as the liners (i.e., they arethicker than 1-2 mils).

By way of example, this simultaneous multi-article thermoforming processcan thermoform a stack that is 3 to 6 layers thick (i.e., 3-6thermoformable plastic layers having appropriate barrier compositionstherebetween) and delivered in roll form. A greater number ofthermoformable sheets (e.g., 10) can also be simultaneously formed andthereafter separated. However, the process can be limited by thethickness of the stack, whereby a stack that cannot practically beheated to a thermoformable temperature within a commercially reasonabletime, without melting exterior layers, or that is too thick to bethermoformed may be impractical. The upper limit on the thickness andnumber of sheets in the stack depends on the materials used in the stacklayers and can both be understood by a skilled artisan in this field andempirically determined through ordinary trial and error procedures. Forinstance, the maximum practical thickness of a stack of materials thatexhibits a relatively low thermal conductivity may be about 50 mils,while the maximum practical thickness of a stack of materials thatexhibits a greater thermal conductivity may be about 70-80 mils. Acoating, adhesive barrier, release agent, or film can be applied to orplaced in between the sheets where needed and in any combination toprevent the sheets from melting/bonding together in the thermoformingprocess, and for allowing the finished products to be separated easily(e.g., a form of silicone may be introduced between the layers of sheetswhile a zone coat of adhesive (e.g., 1 inch wide) may be applied alongthe edge of the substrate). This adhesion allows for easier transport ofthe roll of sheets by keeping the material together in roll form moreeffectively. Multiple sheets of approximate thickness 0.010″ each arestacked together with a barrier/adhesion between each layer. Themulti-sheet layers are rolled together and then sold to variousthermoforming companies. Ultimately time and money are saved by thethermoformers, allowing them to be more efficient. Sheets 90 arethermoformed by being drawn or pressed into a mold 92 having the desiredcavity shape.

Food Service Containers

An important embodiment of the subject matter disclosed herein relatesto peelable food service containers that are made using thethermoformable stack described herein.

For practical uses, food service containers must have sufficientrigidity to contain their intended contents under their intendedconditions of use. For example, cutlery bins can be free standing (i.e.,having the capacity to contain cutlery without breaking or substantiallysagging without the assistance or support of a rack or other frame orcontainer) or held within a rack (in which case, the support provided bythe rack can render the rigidity of the bin relatively unimportant, solong as the bin is sufficiently rigid to contain cutlery without itssides collapsing within the rack and preventing access to its contents).Further by way of example, pans configured to be suspended within a rack(e.g., a wire or shaped metal frame, a countertop, or table top) of abuffet table, sandwich assembly station, or steam table need to besufficiently rigid that they the can support foods that are placedwithin them when installed on the rack without collapsing or fallingthrough the rack. Such suspended food containers typically have a flangeor rim that surrounds one or more cavities defined by the peelablesurface of the container, such that some or all of the weight of thecontainer and its contents is borne by the rack when the container isinstalled therein. Food service containers must therefore be relativelyrigid, the rigidity required being a function of the intended uses ofthe containers and readily understood by skilled artisans in this field.

Food service containers are sometimes used in situations in which heattransfer into of from the food service items therein is desired. Thefood service containers described herein can be used in such situations,with the materials used and number of peelable layers being selected tofacilitate desired or required heat transfer characteristics (e.g.,thermal conductivity and heat capacity of the materials) for thecontainer. Such selection and construction is within the ordinary levelof skill in this field, in view of the disclosure made herein.

Food service containers must also present a sanitary surface forcontacting food service items such as foods, components of foods, andutensils used for preparing or consuming food. Such surfaces must behygienic such that they are free of filth and pathogens which couldpresent health hazards upon contact with food service items. Thesehealth hazards can be physical, microbiological, biological, or chemicalagents of disease. A thorough review of food sanitation is beyond thescope of this disclosure. However, it is recognized that surfaces thatcontact food and other food service items during processing,preparation, storage, serving, and consumption of foods should be freefrom pathogens and potentially pathogenic wastes. Relevant wastes thatshould be excluded include human and animal feces, residues of food thatpreviously contacted the surface, residues of washing and sanitizingreagents, residues from industrial processes for making the container,airborne dirt and grime, mold, mildew, microbial growth (including bothmicrobes themselves and materials on or in which microbes can surviveand reproduce), and contaminants that may contact the surface duringmanufacturing, shipping, handling, and installation of the container.

It is well known to make reusable food service containers from materials(e.g., stainless steel, porcelain, glass, and plastics) that exhibitformability, durability, and resistance to cleaning- andsanitizing-agents. Such containers can be used multiple times andsanitized between uses to maintain the sanitary state of the surfacethat contacts the food or other food service item. By way of example,baking pans and salad bar component trays are often made of metal andtheir food-contacting surface is washed and sanitized between individualuses. It is also well known to make single-use containers having asanitary food-contacting surface, where the container is used only asingle time and discarded. Hybrid products are known, such as bakingtrays having disposable inserts (e.g., paper cups inserted intodepressions in muffin baking trays). Use of disposable liners for foodservice containers not expressly made to receive them is also known,such as when baking dishes are lined with aluminum foil, temperatureresistant plastic sheets, or paper liners.

Reusable food containers have the disadvantage that they must be cleanedand sanitized. Disposable single-use food containers lack thatshortcoming, but can be uneconomical and generate significant amounts ofwaste, since the entire container is discarded following each use. Useof disposable liners in a reusable base mitigates the shortcomings ofboth types of containers, but presents the difficulty of matching orshaping liners to fit the re-usable base. Disposable liners also havethe shortcoming that they must be constructed of relatively thickmaterials in order to facilitate handling and installation. Relative tothe peelable layers of food service containers described herein, suchliners require substantially more polymeric material and energy tofabricate, leading to significantly greater costs. Disposable liners aretypically made by joining one or more sheets of plastic material into abag-like structure, and they include seams that can puncture, tear, offail to join. Furthermore, disposable liners do not adhere to the foodservice container across substantially the entire food-contactingsurface of the container, meaning that tilting or inversion of thecontainer can displace the liner from the container, limiting oreliminating its usefulness.

Disclosed herein are food service containers that have peelable,disposable liners “built in” to a reusable base. Such containers do notrequire matching or fitting of liners and permit multiple uses of thesame base. Furthermore, after the supply of liners is exhausted, thebase can be either reused (i.e., like an ordinary reusable container) orrecycled to make a new container having disposable liners assembledtherewith. Such a peelable, multi-use food service container is believedto represent a substantial advance over existing reusable and disposablefood service containers and liners.

The peelable, multi-use food service container disclosed herein isformed from a relatively rigid sheet of a thermoformable polymer and hasat least one, and preferably a plurality (e.g., 2, 5, 10, or 20) of thinsecond sheets of a polymer peelably attached thereto. Each of the secondsheets can be individually peeled from the container, yielding asanitary surface upon each peeling. The container can thus be reusedrelatively rapidly, since a soiled surface can be sanitized simply bypeeling a second sheet from the surface to expose a fresh, sanitarysurface ready for reuse.

Describing the thermoformable polymer sheet as “relatively rigid” meansthat the container formed from the sheet exhibits sufficient rigidityand integrity to contain food service items without rupturing orspilling its contents under its intended conditions of use. This sheetis referred to herein as the “rigid” sheet to differentiate it from thepeelable “second” sheets, which need not exhibit any significantrigidity.

By way of example, a tray holding sliced meats or cheese during assemblyof sandwiches ordinarily becomes soiled upon contact with the meats orcheese. Prior to reusing the tray, sanitary practice requires cleaningand sanitation of the tray. Where this is achieved by washing, the delayin reusing the tray is typically caused by removing the tray to the siteof washing, by rinsing, washing, rinsing again, sanitizing, and dryingthe tray, returning the tray to the site of use, and refilling. Thisprocess also generates considerable liquid wastes which must be disposedof in a sewer, septic, or other system. If a peelable, multi-use tray asdescribed herein is used in its place, sanitation of the tray can beachieved simply by peeling a second sheet from the tray (optionallywithout even removing the tray from its place at the sandwich-assemblystation or any remaining food or residue from the tray), and the traycan be immediately refilled. The soiled second sheet can be disposed ofwith other solid wastes (e.g., in a wastebasket), and the entireoperation can be performed without the sandwich assembler leaving hisstation.

Thus, in one aspect, the subject matter described herein relates to apeelable, multi-use food service container. The container includes asubstantially rigid sheet of a thermoformable polymer and one or aplurality of second sheets of a polymer, each second sheet having asanitary face and an adhesion face. A first surface of the rigid sheethas a conformation adapted for holding a food service item. Each of thesecond sheets overlaps the rigid sheet at the first surface and conformsto the shape of the first surface. Interposed between the rigid sheetand the adjacent second sheet is a first barrier composition thatadheres (e.g., peelably or permanently) the rigid sheet and the adhesionface of the adjacent second sheet. A second barrier composition(identical to or different from the first) is interposed between theadhesion and sanitary faces of adjacent second sheets. The secondbarrier composition peelably adheres the second sheets to one another.The container thus has a plurality of hygienic second sheets peelablyadhered to a surface adapted for holding a food service item.

In one embodiment, the second barrier composition is identical betweenall second sheets. In another embodiment, a second sheet more distalfrom the rigid sheet is more easily peeled from the second sheetunderlying it (i.e., by using a less tenacious adhesive, or a lowerconcentration of the same adhesive, between the sheets) than is a secondsheet more proximal to the rigid sheet. Alternatively, portions of theadhesive in barrier compositions between more distal second sheets canbe deadened or omitted by applying a non-adhesive barrier composition atthose portions, resulting in a lower force necessary to separate the twoadjacent second sheets.

As with other containers described in this disclosure, the first andsecond barrier compositions can be applied to a single portion of therigid and second sheets or as a grid or pattern of dots (or other shapesand conformations). In an important embodiment, the first barriercomposition is interposed between the rigid sheet and the adjacentsecond sheet over substantially the entire surface of the second sheet.In another important embodiment, the second barrier composition isinterposed between adjacent second sheets over at least substantiallythe entire portion of the first surface. The remainder of the secondsheets in this important embodiment can be free (i.e., grippable), orthey can be adhered to the underlying sheet, especially about theirperimeter, optionally with a tab interposed between the second sheet andthe underlying surface at one or more portions along the perimeter.

The food service containers described herein can have movable orremovable lids that cover an orifice of the container. The lid can besimply a unitary piece of material (e.g., the same material as the rigidsheet) or, alternatively, it can have peelable second sheets adheredthereto in at least the portion of the lid that covers the orifice.

In one embodiment of the food service container, the first surface ofthe rigid sheet is sanitary and the adjacent second sheet is peelablyadhered to the sanitary first face of the rigid sheet. In thisembodiment, the rigid sheet can be permitted to contact the food serviceitem (i.e., because the first surface is sanitary) prior to recycling,discarding, or cleaning and sanitizing the rigid sheet.

In another embodiment, the first surface is not necessarily a sanitarysurface, but the first barrier composition is selected such that thesecond sheet adjacent the rigid sheet cannot be (or cannot convenientlybe) peeled from the rigid sheet under the normal operating conditions(e.g., room temperature) of the container. In this embodiment, the rigidsheet is not intended to be contacted with the food service item duringnormal use, it being shielded therefrom by the adjacent second sheet,which has a sanitary face. Preferably, the first barrier composition isselected such that the adjacent second sheet can be easily removed(e.g., peeled) from the rigid sheet under selected (e.g., relativelyhigh temperature) conditions, such as conditions that would beencountered during recycling of the materials used to make the rigidsheet. In this way, the adjacent second sheet can be segregated from therigid sheet materials and the two materials handled separately. If thefirst barrier composition remains associated with the second sheet, thisalso improves the relative purity of the material used to make the rigidsheet during recycling of that rigid sheet.

The container includes at least one, and preferably two or more, secondsheets. When multiple second sheets are present, the second sheets haveinterposed between them a second barrier composition that peelablyadheres adjacent second sheets to one another. Each second sheet has asanitary face and an adhesive face. When assembled, the adhesive face ofeach second sheet is nearer (more proximal to) the rigid sheet than isthe sanitary face. Thus, for adjacent second sheets, the sanitary faceof the more proximal second sheet is nearer the rigid sheet than is theinterposed second barrier composition, which itself is nearer the rigidsheet than is the adhesive face of the more distal second sheet. Thecharacteristics of each of the sanitary face of the more proximal sheet,the interposed second barrier composition, and the adhesive face of themore distal sheet is selected so that when the more distal sheet ispeeled away from the more proximal sheet, the second barrier compositionremains substantially (preferably virtually exclusively) with theadhesive face of the more distal sheet. This leaves a sanitary face thatis substantially free of the second barrier composition. Because thesanitary face is substantially free of the second barrier composition,potential interactions between that second barrier composition and anyfood service items placed in the container are minimized. This can beachieved, for example, by controlling the surface energies (e.g., byselecting materials in multi-layer composite second sheets or by coronatreatment or other surface treatments of the second sheets) of thesanitary and adhesive faces of second sheets such that the difference insurface energy between the two faces is at least about 5 Dynes.

The container can have one or more tabs associated with the secondsheets. The tabs can, for example, be interposed between adjacent secondsheets for facilitating separation of the adjacent second sheets. In oneembodiment, the tab is interposed between adjacent second sheets andsimply prevents the two second sheets from tightly adhering to oneanother (i.e., regardless of whether one or both second sheets adhere tothe tab). The tab creates a region at which the adjacent second sheetscan be manually separated from one another. In one embodiment, the tabadheres to the adhesion face of one of a pair of adjacent second sheets,but does not adhere to the sanitary face of the other adjacent secondsheet. If the second sheets are cut across the area including the tab, auser can pull the two second sheets apart by grasping the tab and thesecond sheet to which it adheres and pulling these away from the othersecond sheet (to which the tab does not adhere). If desired, the usercan insert an object (e.g., the tip of a fingernail or a knife) betweenthe tab and the non-adhered second sheet to facilitate the separation.

The tab can also extend beyond the edges of one or both second sheets,which provides a convenient surface for grasping and pulling by a user.In a food service environment, however, tabs that extend beyond thesanitary surfaces of second sheets can provide opportunities for soilingand cross-contamination between layers of second sheets, and it isrecognized that tabs that are not obscured by an over-lying second sheetare not appropriate for all food service uses. In such situations, tabsare preferably completely overlaid by a second sheet or, at least, donot extend beyond the edge of an over-lying second sheet.

For food service containers, it is desirable to maintain a clean andsanitary face on an underlying surface prior to when an overlying secondsheet is peeled therefrom. Separation or peeling of an overlying secondsheet during manufacture, shipping, or storage offers an opportunity forenvironmental contaminants to contact the underlying surface. Tabs thatare not adhered to both an overlying second sheet and the underlyingsurface present an opportunity for such separation or peeling to occur.In order to prevent this, tabs are preferably adhered to both overlyingsecond sheet(s) and the underlying surface in the food servicecontainers described herein. Tabs should be peelably adhered to at leastone of the adjacent surfaces, to facilitate peeling of second sheets(and, optionally, the tabs).

In one embodiment, a container having multiple second sheets has tabsinterposed between those second sheets to facilitate their peeling fromthe container. Each tab is peelably adhered to one of the adjacentsecond sheets, preferably at least along substantially the entireportion of the tab that is overlapped by that second sheet. The tab isalso adhered (either peelably or relatively fixedly, such as by fusionor tenacious adhesion) to the other adjacent second sheet, againpreferably along substantially the entire portion of the tab thatoverlaps that other second sheet. Such an arrangement facilitatespeeling of a second sheet from the container, either by peeling a secondsheet from the tab and thence from the container or by peeling the tabattached to an overlying second sheet away from an underlying secondsheet and using the partially peeled tab as a handle to peel theoverlying sheet from the underlying sheet. If the tab is peelablyattached to both adjacent second sheets (either with equal or unequaltenacity), then one second sheet can be peeled from the other by aid ofthe tab, and the tab can thereafter be peeled from the second sheet towhich it remains attached.

By way of example, a tab can be peelably adhered across its entiresurface to a portion of a proximal (relative to the first sheet) secondsheet near one edge of the container and peelably adhered across onlythe overlapping portion of a distal second sheet that overlaps the tabat one edge of the distal second sheet. In this conformation, the gapbetween the proximal and distal second sheets contains the tab at theedge of the distal second sheet and is sealed both above and below thetab by the peelable adhesive (the second barrier composition). Thus, thegap resists introduction of contaminants between the proximal and distalsecond sheets prior to peeling of the distal second sheet. The distalsecond sheet can be peeled from the proximal sheet by drawing aninstrument (e.g., a fingernail or the edge of a spatula) across the edgeof the distal sheet where it overlaps the tab, thereby initiatingpeeling of the distal sheet from the tab. By pulling on the distal sheetusing the thus-displaced edge thereof, the distal sheet can be peeledfrom the container, leaving the proximal sheet attached thereto, withthe tab remaining attached to the proximal sheet. If desired, the tabcan be peeled from the proximal sheet.

When tabs are included in a container as described herein, the tabs canbe aligned with one another, such that peeling of one second sheet andits associated tab reveals another tab located at the same location onthe container (albeit one second sheet-layer closer to the rigid sheet).However, this aligned arrangement of tabs can cause difficulty, in thata user desiring to peel only the upper-most second sheet (i.e., the onemost distal from the rigid sheet) may inadvertently disturb multiplesheets while attempting to manipulate only the tab associated with theupper-most sheet. This difficulty can be avoided if the tabscorresponding to different second sheets are placed at differentlocations along (or near) the perimeter of the container. If these tabsare physically separated from one another (e.g., tabs separatedleft-to-right, when viewing the container from the distal surface), auser may be able to more easily manipulate only the tab corresponding tothe upper-most second sheet without disturbing the tabs (and thesanitary surface) corresponding to other second sheets.

The tabs can be the same color and composition as a second sheet andcan, in fact, be simply an extension of one of the second sheets (i.e.,the second sheet that is peeled when the tab is pulled). However, tabsare preferably made a different color and from a different material, sothat they can be more easily identified and manipulated by a user. Inone embodiment, each tab is made from a material that is different incolor from and attached to the adhesion face of the second sheet that ispeeled upon pulling the tab. One or more of the tabs can also include anindicium of the number of second sheets that remain attached to thecontainer. By way of example, each second sheet can have a tab attachedto the adhesion face thereof, with the tab bearing a numeral equal tothe number of second sheets that remain adhered to the rigid sheet uponpeeling the sheet to which the tab is attached. By way of an alternativeexample, all tabs can be white, with the tab associated with the secondsheet that is adjacent the first sheet being red or bearing a star, thetext “Last Use,” or the like.

As with the tabs, the colors of the rigid and second sheets areimmaterial, yet selectable. In instances in which either the rigid sheetor the second sheets will be viewed by customers (e.g., at a sandwichassembly station at a restaurant in which customers stand within view ofthe station), it may be desirable to select sheets having particularcolors (e.g., matching the decor of the restaurant) or appearances. Inone embodiment, the rigid sheet has a color selected for a particularpurpose (e.g., consistency with the color scheme of a food servicestation such as a buffet table), and the second sheets adhered theretoare substantially clear, so that the container has substantially theappearance of the rigid sheet, regardless of how many second sheetsremain adhered thereto. For functional reasons (e.g., keeping track ofhow many peelable layers remain), it can also be desirable to impart acolor or appearance to different layers of the container. By way ofexample, if it is desired that the rigid layer not be used to contactfood service items, then the rigid layer can be made from materialshaving one color (e.g., black), while the second sheets that arepeelably adhered to the rigid sheet are made from materials having adifferent color (e.g., white). Thus, in this example, if a white surfaceis revealed upon peeling a second sheet, the user knows that therevealed surface is that of a desirable second sheet, while the userknows that if the revealed surface is black, then the revealed surfaceis the non-desired rigid sheet. Although printing is generally not usedon surfaces used for food contact, the printing methods described hereincan nonetheless be used to print images, text, or other indicia on thesecond sheets of the container described herein.

Food service containers are sometimes intended to facilitate heattransfer either into or away from food service items held in thecontainer. By way of example, forks held in a compartment at a salad barare often chilled, as are lettuce, dressings, and other saladcomponents. Soups, cooked entrees intended for consumption while warm,and steam tray contents are often heated. Other components (e.g.,crackers and breads) may be neither heated nor cooled. Such heating andcooling is typically effected by contacting a fluid (e.g., air, steam,or water) against the surface of the container on the face opposite theface that contacts the food service item contained therein.

Where heating or cooling of container contents is desired, the materialsused to make the food service container should be selected to facilitatethe anticipated operating conditions and the desired heat fluxcharacteristics. Thus, in situations in which relatively high heat fluxis desired, materials which have relatively high thermal conductivityshould be used and the number of second sheet layers should becontrolled. Selection of appropriate materials is both within the ken ofthe ordinary designer and determinable through routine empiricalobservation.

A wide variety of polymer materials may be used to form the rigid andsecond sheets for food service containers as described herein. Selectionof appropriate materials is within the level of skill of an ordinaryartisan in the field of thermoforming. An important consideration whenselecting materials for use in food service containers is statutes,regulations, and other requirements that are relevant to materials usedin contact with food in the locale in which the container is to be used.By way of example, in the United States, materials used to contact foodduring manufacture, shipping, storage, and preparation are regulated bythe Food and Drug Administration's Center for Food Safety and AppliedNutrition. In addition to processes for applying for approval forcontacting food service items with various materials, most relevantregulatory agencies maintain lists of materials that are generallyapproved for use in contacting foods. In the U.S., such materials arereferred to as “Generally Regarded as Safe” (GRAS), and lists of GRASmaterials for food contact substances are maintained by the U.S. Foodand Drug Administration. Many of these materials can be used to make therigid and second sheets and barrier compositions described herein.

Materials useful for making the containers described herein can also beselected from materials identified and/or described by private ornon-profit standard-setting organizations (e.g., NSF International ofAnn Arbor, Mich.), that report or recommend materials safe for contactwith food and food-preparation surfaces.

Likewise, a wide variety of barrier compositions can be used in the foodservice containers described herein. The barrier compositions shouldprovide sufficient adhesion between the second sheet and the underlyingsheet that the second sheet is not disturbed or peeled by normal aircurrents and handling operations. It is sufficient, for example, if thebarrier composition provides only sufficient adhesive strength to keep asubstantially rigid peelable sheet from falling out of the containerwhen the container is inverted. At the same time, the adhesion providedby the barrier compositions must not be so great that the second sheetcannot be peeled from the underlying surface without damaging the secondsheet or the underlying surface. The barrier compositions should also beselected for chemical and physical compatibility with the food serviceitems and environmental conditions that the containers are likely toencounter. By way of example, barrier compositions intended for use infood service containers for holding hot soup should maintain theiradhesive properties at anticipated soup temperatures, should notsubstantially dissolve in aqueous fluids (i.e., in the event the soupcontacts the barrier composition near an edge of or through a breachthrough a second sheet), and should preferably be peelable both atanticipated soup temperatures and at 20 degrees Celsius. A variety ofGRAS barrier compositions are available and, provided they conform withthe other characteristics described herein, suitable for use in thecontainers.

For containers intended for use in contact with consumable food items,good manufacturing processes, consistent with practices common in thefood industry for maintaining sanitation, should be used to make,package, ship, store, and use the food service containers describedherein.

In an important embodiment, the food service container has astandardized shape and conformation. Standardized containers are used ina wide variety of settings in the food and restaurant industries.Examples include salad bars, sandwich assembly stations, steam tables,chafing dishes, cafeteria serving counters, cafeteria utensil stands,and buffet tables. The sizes and conformations of food servicecontainers used in such settings are widely known and often vary bymanufacturer of the setting furniture. An advantage of the food servicecontainers described herein is that they can be manufactured to fitsubstantially any known standardized racks or furniture. They can alsobe used to form free-standing containers, such as baking pans, servingtrays, and cookie sheets.

The food service containers described in this section are made insubstantially the same ways as other containers described in thisapplication (except that more sanitary manufacturing requirements may benecessary than are used, for example, for making paint trays). Forrelatively shallow containers (e.g., those in which the most-displacedportions of the thermoformed stack are displaced only 1-2 inches fromthe pre-thermoforming position of the stack), standard thermoformingapparatus and procedures are appropriate. For deeper containers (e.g.,those in which one or more portions of the thermoformed stack aredisplaced >6 inches from the pre-thermoforming position of the stack orin which relatively steep sides are formed), standard thermoformingmethods can lead to creasing, overlapping, excessive thinning, puncture,or some combination of these, of one or more sheets in the stack,including the relatively thinner second sheets. To avoid this, it isdesirable to control the conformation of the stack during the formingoperation, so that when the stack is engaged by the thermoforming mold,it is not creased, folded, excessively thinned, or punctured.

In one method of controlling the conformation during forming, a stackincluding the rigid sheet and multiple second sheets is assembled andheated to about a temperature appropriate for thermoforming. Prior toengaging the heated stack with the thermoforming mold, pressure(negative or positive) is applied to one face of the stack, so that thestack is deflected by atmospheric pressure into a shape that roughlyapproximates the shape of the thermoforming mold while maintaining thestack in a smooth conformation. The pressure is preferably applied byadjusting the atmospheric or the gas pressure at the stack face, forexample by applying a vacuum. Apparatus for applying such pressure arewell known and include, for example, devices commonly referred to as“vacuum boxes” and “pressure boxes.” Any apparatus used to apply suchpressure preferably does not physically contact any portion of the stackthat is to be thermoformed (to avoid heat transfer that would affect thethermoformability of the contacted portion). After the stack has beenpressure-deformed, the stack is contacted with one or more thermoformingmolds, per normal thermoforming procedures. As in standard thermoformingprocedures, the stack can be drawn against a mold by application ofnegative pressure on the face of the stack that contacts the mold,forced against a mold by application of positive pressure on the faceopposite that which contacts the mold, or both.

In one embodiment of the food service containers described herein, therigid sheet is made from a recyclable polymeric material, while thesecond sheets are made from thin, disposable polymer that preferablydegrades relatively quickly in landfill conditions. This embodimentrelates to a container that significantly reduces waste generationcorresponding to use of food service containers. Each second sheet canbe simply discarded with solid wastes (i.e., garbage) after use. Therigid sheet that supports the second sheets can be recycled, eitherthrough a municipal recycling service provider or by returning it to themanufacturer to be re-melted and again formed into rigid plasticsheeting (or other materials for which recycled food containers may bemore appropriate). In one version of this embodiment, the first barriercomposition is selected such that it relatively tightly adheres theadjacent second sheet to the rigid sheet, so that that adjacent secondsheet cannot be easily removed from the rigid sheet during normal use.When returned to a recycler, the adjacent second sheet (which may besoiled from use) can either be recycled together with the rigid sheet(especially if it is made of the same polymer as the rigid sheet) or itcan be removed by subjecting the container to a condition (e.g., hightemperature) at which the first barrier composition adheres the adjacentsecond sheet less tenaciously to the rigid sheet, permitting removal ofthe second sheet prior to recycling of the rigid sheet. In thisembodiment, the level of impurities in the recycled rigid sheetmaterials can be significantly improved by removing the potentiallysoiled second sheets therefrom.

The peelable, multi-use food service container described herein can beused as a component of a food service station, such as a salad bar or asandwich assembly station. In such a station, a rack, countertop, orother apparatus has a conformation adapted to hold at least one peelablecontainer. The station can, of course, hold multiple peelable containersof the same or different sizes and shapes. In normal food storage anddispensing operations, such a station is essentially indistinguishablefrom stations having non-peelable containers. However, when cleaning orsanitation of one of the containers is desired, a difference becomesapparent. Rather than removing a container and either replacing it withanother container or washing and replacing the same container, as in atraditional station, a peelable container can be cleaned and sanitizedsimply by peeling a second sheet from the first surface thereof. Thepeeled container can thereafter be refilled and immediately re-used,with the peeled sheet discarded. The cleaning and sanitation achieved bypeeling both improves the rapidity with which the station can bemaintained and reduces the waste associated with maintaining it.

In some instances, containers at food service stations are refilled in akitchen or other food preparation area prior to being brought to thestation to replace soiled containers. In such instances, the peelablecontainers described herein can nonetheless be advantageous, in thatthey reduce the time and waste associated with cleaning soiledcontainers, whether that cleaning is performed at the station itself orin a kitchen or other preparatory area.

In another aspect, the disclosure relates to method of operating a foodstation. The method involves assembling one or more first food productsfrom components stored in multiple food containers, including at leastone selected component that is held in a peelable food containerdescribed herein. After assembling first food product(s), a second sheetis peeled from the peelable food container (revealing a sanitary surfacethat can be contacted with fresh food components), and more of theselected component is added to the peelable food container. One or moresecond food products (identical to or different from the first foodproducts) are then assembled from components stored in the foodcontainers, including at least the selected component.

The peelable food service containers described herein will typically bemanufactured at a site distant from the location at which they will beused, transported between the manufacture and use locations, and storedat one or more intermediate locations. At each of these steps, thecontainers can be exposed to environmental contaminants (e.g., dirt,dust, rodents, liquids) that are not compatible with maintenance ofsanitary surfaces. When a peelable food service container as describedherein is contacted with such contaminants, the outermost second sheet(i.e., the one which will have contacted the contaminant) can simply bepeeled off to remove the contamination and reveal a fresh, sanitary faceuseful for food service. However, it is preferable to avoidmanufacturing, storage-, and transportation-contamination in the firstplace.

In order to prevent contamination of the sanitary face of the outermostsecond sheet, the containers can be packaged in a wrapper, box, or thelike. Alternatively, a protective coat layer can be included as theuppermost (i.e., most distal from the rigid sheet) layer in the stack.The protective coat should overlap the uppermost second sheet, at leastover the first surface (i.e., the portion of the uppermost second sheetthat will contact food service items), and should be relatively easilyremovable therefrom, for example by peeling or rinsing with water.Because the purpose of the protective coat is simply to prevent contactbetween environmental contaminants and the uppermost second sheet, thecomposition, color, and thickness of the protective coat are notcritical, and any relatively inexpensive material can be used. Theprotective coat contacts the uppermost second sheet over substantiallythe entire sanitary face of that second sheet. The protective coat canbe held in place simply by electrostatic attraction, and is preferablypeelably adhered to the second sheet. The protective coat can also bemade from a material that resists scratching, whereby the protectivecoat can protect the container from both contamination and physicaldamage. The protective coat material can be selected such that it can beprinted upon or accepts adhesive labels, so that the protective coat canprovide both shielding and marketing or labeling functions. Theprotective coat can be peeled from the container and discarded (orrecycled) by the user prior to filling the container with a food serviceitem for the first time.

Example

A food service container designed to be inserted into a rack for holdingmultiple food service containers as a part of a sandwich assemblystation was fabricated. The concave interior portion of the containerhad the approximate conformation of a tapered rectangular cuboid havingrounded edges and dimensions of about 10½ inch length (tapering to about11¾ inch at the opening)×about 4¾ inch width (tapering to about 5¾ inchat the opening)×5½ inch depth. The corners of the interior cuboid hadradii of about ⅞ inch. A flange extended about the opening, having alength of about 12¾ inches and a width of about 6⅞ inches, with roundedcorners (about ¾ inch radius).

In this embodiment, the rigid sheet was composed of PET (polyethyleneterephthalate), black in color, approximately 30 mils (i.e., ca. 0.03inch) in thickness. The container included ten second sheets peelablyadhered to the rigid sheet. Each of the second sheets was composed ofpolyethylene, was white in color, and approximately 2 mils in thickness.Interposed between each of the second sheets was a second barriercomposition that was composed of a water-based acrylic pressuresensitive adhesive, which was flood coated on the adhesive face of eachsecond sheet. A first barrier composition identical in composition tothe second was interposed between the rigid sheet and the adjacentsecond sheet, and was present by virtue of the adhesive face of theadjacent second sheet having been flood coated therewith.

Tabs were interposed between at least several pairs of adjacent secondsheets at one of the corners of the flange. The tabs extended diagonallyacross the corner of the flange and were trimmed flush with the edges ofthe second sheets between which they were interposed. Each tab waspeelably adhered to the second sheet that overlaid the tab and was notadhered to the second sheet beneath (i.e., more proximal to the rigidsheet) the tab. Second sheets could be peeled from the container byscratching or picking at the tab beneath the uppermost second sheet tobegin peeling the tab and uppermost second sheet from the second sheetunderlying them. By pulling the sheet and tab approximately across thecavity in the container (i.e., generally tangentially across the top ofthe container), the uppermost second sheet could be peeled therefromwithout substantially disturbing any of the other second sheets of thecontainer. This could be done multiple times, once for each of thesecond sheets of the container. The lowermost second sheet couldsimilarly be peeled from the rigid sheet.

The appropriateness of the container for holding and storing foodservice products was tested by pouring food products with easilydetected residues (i.e., pickles with brine, oils, etc.) into the cavityof the container, permitting them to remain there for about one day, andthen removing the food products. Upon peeling the second sheet thatcontacted the food products, no residue could be detected by itscharacteristic scent or by wiping the interior of the cavity afterpeeling the top sheet. This confirmed that the containers so testedcontained the food products without permitting them to leak after about24 hours—a longer period than the normal period of storage for foodservice containers of this type in, for example, a buffet or steamtable.

Certain modifications and improvements will occur to those skilled inthe art upon a reading of the foregoing description. It should beunderstood that all such modifications and improvements have beendeleted herein for the sake of conciseness and readability but areproperly within the scope of the following claims.

1. A peelable, multi-use food service container comprising a relatively rigid sheet of a thermoformable polymer, wherein a first surface of the rigid sheet has a conformation adapted for holding a food service item; at least one second sheet of a polymer, each of which overlaps the rigid sheet at the first surface and conforms to the shape of the first surface, each second having a sanitary face and an adhesion face; a first barrier composition interposed between and adhering the rigid sheet and the adhesion face of the second sheet adjacent the rigid sheet; and, if the container comprises more than one second sheet, a second barrier composition interposed between and peelably adhering the adhesion and sanitary faces of adjacent second sheets, whereby each of the second sheets is peelably removable from the container.
 2. The container of claim 1, comprising a plurality of the second sheets. 3-7. (canceled)
 8. The container of claim 1, wherein the first barrier composition peelably adheres the rigid sheet and the adhesion face of the second sheet adjacent the rigid sheet.
 9. The container of claim 1, wherein the first surface is sanitary.
 10. The container of claim 1, comprising at least three second sheets.
 11. The container of claim 1, comprising at least six second sheets.
 12. The container of claim 1, comprising at least ten second sheets. 13-16. (canceled)
 17. The container of claim 1, further comprising a protective coat that removably overlaps the second sheet most distal from rigid sheet at over the entire first surface.
 18. (canceled)
 19. The container of claim 1, having a conformation adapted to fit within an orifice defined by a rack.
 20. The container of claim 19, having a conformation wherein a cavity defined by the first surface extends into the orifice and a flange surrounding the cavity engages the rack. 21-25. (canceled)
 26. The container of claim 1, having the conformation of a generally rectangular pan.
 27. The container of claim 1, having the conformation of a generally circular pan.
 28. The container of claim 1, wherein the adhesion face of the second sheets, the sanitary face of the second sheets, and the second barrier composition are selected such that the second barrier composition adheres selectively to the adhesion face, relative to the sanitary face, of adjacent second sheets. 29-35. (canceled)
 36. The container of claim 1, wherein the rigid sheet is made of a material selected from the group consisting of polyethylene terephthalates, high density polyethylenes, high molecular weight polyethylenes, polypropylenes, polystyrenes, polyvinyl chlorides, copolymers of these, and combinations of these.
 37. The container of claim 1, wherein each second sheet is made from a material independently selected from the group consisting of polyethylenes, polypropylenes, polyethylene terephthalates, nylons, polyvinyl chlorides, copolymers of these, and combinations of these. 38-42. (canceled)
 43. The container of claim 1, further comprising a movable lid adapted to cover a recess of the container that abuts the first surface.
 44. (canceled)
 45. A food service station comprising a rack having a conformation adapted to hold the container of claim
 1. 46. The station of claim 45, wherein the rack has a conformation adapted to hold a plurality of containers of claim 1,
 47. (canceled)
 48. A method of operating a food station, the method comprising assembling a first food product from components stored in the multiple food containers, including at least a selected component stored in the peelable food container of claim 1, peeling a second sheet from the peelable food container, adding more of the selected component to the peelable food container, and assembling a second food product from components stored in the multiple food containers, including at least the selected component. 49-51. (canceled)
 52. A method of maintaining sanitation of a food station, the method comprising storing multiple food service items in the food station, wherein a plurality of first food service items are stored in the peelable container of claim 1, dispensing at least one of the first food service items from the food station, removing any remaining first food service items from the peelable container, peeling a second sheet from the peelable container, and thereafter storing additional first food service items in the peelable container. 53-88. (canceled) 